whereas, with paddle-wheels, the sailing " that any two bodies, when sufficiently power (from the cumbrous nature of the

near, impress their image one on the paddle- boxes and the immersion of the other, although both be in absolute dark. see wheel, with the wind abeam,) is of ness.' Having devoted many years to little value.

the endeavour of tracing the con6th. The weight of the propeller is nexion of photic matter with the elenot one-tenth of the paddle-wheels and ments, I beg leave, on this occasion, to their boxes.

submit to your readers the following ge7th. The beautiful appearance, and neral observations. snug and safe rig of a sailing vessel is The only clue which I have been able preserved by using the funnel as the to find to the chemical affinities of the mizen mast.

inorganic elements, capable as they 8th. A saving of nearly 20 per cent. in are of attracting, reflecting, and conductfirst cost, when equipped and ready for ing heat, and of undergoing manifold

atomic metamorphoses without destruc9th. A saving of at least 50 per cent. tion, is the hypothesis, that they must in disbursements.

respectively consist of congerated inert 10th. Room for carrying nearly double radicals, chemically saturated with such the amount of passengers and cargo, thus proportions of imponderable, yet material increasing the returns cent. per cent. photic fluids, as certain laws of nature

11th. The power of instantly discon allowed them to bind or appropriate to necting, shipping and unshipping, the themselves, so as to constitute the existpropeller.

ing diversity of apparently simple eleFrom all the preceding advantages it ments, while the very same fluids also can require no argument to prove, that abound in a vivid state. We cannot any the time has come, when vessels, worthy longer doubt that the photic sunbeams the name of ships (and not boats, as the are fraught with radical elementary present race of steamers are properly de matter,--similar to the chemical flame nominated,) may be usefully and econo of terrestrial fire, but much sublimer and mically employed in carrying her Ma

purer; and we may be justified in prejesty's mails with safety and despatch ; suming that they deposit such radical and that we may now use steam, when matter on the terrestrial globe, saturated necessary only, that is to say, in adverse

with photic fluids, capable of being fixed vinds or calmns, retaining therewith the

in a process of condensation, after concapability of laying aside steam, and using tamination with terrestrial effluvia. We the old-fashioned and cheaper power, "the have next to consider that the terrestrial winds of heaven” whenever they blow globe, with its gaseous atmosphere, is from the right quarters, instead of being

encompassed by a subtile universal ether, compelled, in such cases, to consume our and may fairly assume that the latter fuel and work our engines for no other pervades the whole ponderable and porous purpose than that of preventing the in elementary mass. This omnipresent ether active wheels from performing the office

must be an inert imponderable fluid, itself of a drag to the vessel's sailing velocity. saturated with the still finer photic fluids, I am, Sir, your obedient servant, diffused through it by the sun, and is thus

H. WIMSHURST. their omnipresent conductor, preserving a 2, Cowper's-court, Cornhill.

vivid store, always ready to act upon the ponderable elements by affinity with their fixed photic constituents. Such I


sume to be the constitution of our earth GRAPHY, AND NEW THEORY OF THE

and all the planets, subject to the regu.

lative and fostering influence of the sun. Sir, -The account published in your The photicated ether in question, Journal, of Dr. Möser's photographic which I presume to pervade .all nature, experiments, is highly interesting to me, has not yet been recognized as being as indicating the approach to the recog identical with the fine fluid contents of nition of the existence of photic fluids. what we term vacuum. I consider that It includes, I think, what Mr. Hall has it is identical therewith; and if the atomic termed “Thermography," namely, the theory be reduced to the plain proposinovel phenomenon noticed by Dr. Möser, tion, that all ponderable matter consists




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of vesicular, more or less porous, perfo- ether, of negative-brightness or radiancy rated and elastic molecules, however mi a predominance of positive, photic fluids. nute and singly invisible, some being Whichever order of fluids is predominant, more expansible than others at a given combats and repels the other, absorbing temperature ; it is reasonable to assume and neutralizing a certain residuum, so also, that, whether contracted or expand that neither is under any circumstances ed, their central vacui, as well as the in totally absent. The sun's radiance is a terstices between the atoms, must be re constant emanation and a re-attraction of plete with the said photicated ether, on chemical electromagnetic currents, rethe same principle on which air would transmitted from the surfaces of the replenish and encompass a heap of any planets, in whose atmospheres they cause hollow, perforated, and elastic globules. atomic vibration or undulation with I have further come to the conclusion, that brightness. In the sunbeams travelling positive and negative electricity, positive along, their positive ingredients are foreand negative magnetism, are identical with most, the negative following in the four distinct photic fluids, discernible wake; when hitting their object, they under certain circumstances, particularly combine and intermix ; the surface, the in the body of a flame, by the blue, red, globe, absorbs less of the former than yellow, and the colourless or water hues,

of the latter ; thus a greater proporwhile the analysis of the sunbeams also ex tion is thrown back of the positive than hibits negative (black) and positive (white) of the negative, to cause atmospheric rays. We should thus obtain six distinct heat and undulation. By concentration photic fluids, of which the last named two of the sunbeams in burning glasses we have no polarity in combination, but do have learnt to obtain solar fire; this was alternately precede or lead, and may ab the first, and I deem it the greatest of sorb the first named galvanic four. Let the great discoveries that have been made us also postulate, that in combination with down to photography, by which it is now the ether, positive electromagnetism con proved, that all material bodies have constitutes latent heat, and negative elec stant photic halos of their own, radiating tromagnetism-latent cold, and we may even invisibly and insensibly, “ in darkfinally infer, that a concentration of the ness as well as in brightness," and caformer around a combustible, or in the pable of making impressions upon each galvanic spark, is the radiating and con other. This can only be owing to the ductible heat (diffused by gaseous fire or

affinity between the fixed photic ingreflame) by which organic bodies are dis dients of the elements and the vivid omsolved-their ponderable atoms being se. nipresent photicated ether. And what parated, expanded or rarified, rendered does the polish of metals, the brilliancy volatile and caused to float about, until of precious stones bespeak ? refrigerated and recontracted by contact If you can kindly spare a page in your with cold, so as to reconstitute themselves valuable journal for this letter, you will into inert elementary congeries. The greatly oblige, heated ether is thus in the expanded Sir, your most obedient servant, atoms, what gas is in a balloon or air in

Z. a bladder. There is more latent heat in London, December 31, 1842. a vacuo, than in the air surrounding the receiver; and gases, when compressed, evolve heat—some also say, light.

The formation, growth and putrefac Sir,- In the November Part of the tion of organic bodies is effected by slow Mechanics' Magazine I perceive that a atomic vibration or combustion at a low correspondent, J. F. B., is still of opitemperature; this process is incessantly nion that sand cannot be used for tampgoing on in nature; it is the destiny of ing. I beg to mention, for the informawhat we call matter. The laws of this tion of others, that I have most successprocess involve the important, yet un fully used sand for that purpose. solved question of elementary destructi The experiments have been tried in a bility, which I do not wish to touch now, stone-quarry. A hole, 2 inches in diaas it would lead me too far,

meter and 5 feet deep, was made in the On the same principles, darkness would rock. Half the charge was first put into be owing to a vivid predominance in the the exploding cartridge, and next the


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EXPLOSION OF THE AMERICAN STEAMER MEDORA." remaining half of the powder; then a

them to support the plates. Through tight oakum wad was put down, leaving the centre of the wooden discs passes a a space of 5 or 6 inches between it and

strong wooden axle, which rests on the the powder: the hole was filled up with ends of the wooden trough, and only alfine dry rabbit sand, to the depth of 15 lows the plates to be within half an inch inches.

of the bottom of the trough. By turning The sand was not blown out, and the a handle, the axle and plates are made to result was quite satisfactory.

revolve, and can be immersed in the The battery I make use of consists of acid, or turned out of it, with the greatest 48 pairs of copper and zink semicircular facility. plates, 8 inches in diameter : the plates I remain, Sir, your obedient servant, are fitted to a suitable frame, with eight

H. M. wooden discs, with rails mortised into Wexford, December 28, 1842.

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THEORY OF NUMBERS. Sir,---In Barlow's “Theory of Num almost called an axiom, I have endeabers, a work I have lately begun to voured to prove it in a shorter way, and read, there is (Propos. 9) rather an ela shall be glad to know, through the meborate demonstration of the proposition : dium of your valuable publication, wheThat the product of any two numbers is ther the following demonstration is conthe same, whichever of the two is the sidered a satisfactory one. multiplier. Legendre, in his Theorie

If a and b are the two factors, call des Nombres, gives, I believe, a similar

a6 demonstration ; and as the truth of it ap a6 = x, 6ary, then

6α pears to me so evident, that it might be

1 1
6 1


1 Now,

= a xlx = a ×

1 ; whence,

x=y and ab=ba. Q. E. D. Which rea is the only solid foundation of the sub-
soning may evidently be extended to any jects your Journal so ably treats of,
number of factors.

would be greatly benefited by smoothing I hope I am not intruding in address the way as much as possible, consistently ing these lines to you; if I am not, I with sound reasoning; though, at the may perhaps take the liberty of address same time, I am well aware that a ing you again, from time to time, on si. royal road” to knowledge does not milar subjects, offering more difficulties exist. to the student who is beginning pure I have the honour to remain, Sir, mathematics, and some of which he may

Very respectfully, be unable to surmount without the aid of a master. I cannot help being of opi.

A LOVER OF SCIENCE. nion, that the important science, which City, December 24, 1842.




“ MEDORA." Practical Conclusions in respect to Tubular Boilers. [From Memoir in the Journal of the Franklin Institute, by Benjamin H. Latrobe, Esq., C.E.*] Upon the 14th of April, 1842, the Medora, Her fire was lighted at about 2 o'clock, a new steam-boat, built by a company, to p. m., and about an hour after, the agent run between Baltimore and Norfolk, was and some of the proprietors came on board, prepared for a trial trip down the Patapsco.

and she prepared to start. There were pro. She lay at the engine-builder's (John Watch bably between 50 and 100 persons in her man) wharf, on the south side of the Basin. when she started, many of whom were work

men connected with her construction; and • The original of this very interesting memoir is

as on such occasions these persons, each illustrated by a number of very accurate engrav.

deeming himself to be magna pars of the af. ings; but, as the parts here extracted by us are suf

fair, are prone to intermeddle, there was ficiently intelligible without them, they are omitted. -Ed. M. M.

much crowding and confusion about the en




gine, and its proper management by the en by diagonal bars and rods, and above the gineman was not unlikely to be interfered tubes were one or two rows of longitudinal with. The pride of the workmen in the ex rods, of one inch diameter, going from the pected performance of the boat would natu forward to the after head. The sheets of the rally dispose them to do all they could to boiler were of the usual thickness of oneaccelerate her speed ; and the suspicion quarter of an inch, and do not appear to afterwards expressed, that undue means were have been of bad quality. There were two employed to increase the pressure of the fire-doors in front, for the introduction of steam, was not unreasonable. It has also, the fuel into the spaces between the legs ; indeed, been supported by sufficient testi and in the sheet-iron composing the front of mony, though at the same time contradicted, the smoke-chamber supporting the chimney I am told, by one of the surviving witnesses stack, there was a small, movable, circular of the calamity.

door opposite each tube, for the insertion of The boat had just cast off her lines, and, an instrument to clean the flues when rein backing out, had made one or two revo quired. The number of gauge-cocks was lutions of her wheels, when her boiler burst. four, the lowest being a little above the level Five-and-twenty persons on board were of the highest row of tubes. The safetykilled or mortally wounded; the upper, or valve was placed upon a drum near the top promenade deck, over the boiler, was blown of the boiler, and was, as will be seen herein fragments into the air, and the forward after, of large dimensions. part of the hull so shattered, that she im Such was the boiler in all its parts; and mediately sunk, in ten or twelve feet water. its unusual size and bold design must be Her engine, except in its connexion with the striking to every observer. boiler and the after part of the hull, was un. An examination of the wreck of the boiler, injured. The boiler was placed forward of as it still stands in the yard of Mr. Charles the wheel-houses, standing fore and aft in Reeder, engine-builder, clearly shows that it the hold of the vessel, and rising up through first gave way where the legs unite with the the main, to within three or four feet of the belly, and where the removal of so much of upper deck. It was thrown upwards to the the metal reduced the strength of the cylinheight of the top of the engine-beam, or der to its minimum. The explosion was more than thirty feet, and while in the air it downwards, carrying away the right-hand, turned, so as to fall upon its side, exactly or starboard leg, and the middle one, and crosswise of the boat. Circumstances con tearing into shreds the inner sheet of the nected with the escape of the steam and larboard leg, at its junction with the cylinwater, and the resistance of the wood-work der. The escape of the steam and water, of the upper deck, no doubt, caused this principally on the starboard side, probably singular rotation.

caused that side to revolve vertically in the The boiler consists of a cylinder eleven rise of the boiler into the air, and thus would feet in diameter, and nineteen feet long, sup have made it fall upon its larboard side in ported on three legs, of the same horizontal the descent, while at the same time a hori. length, and composed of sheets of five and a zontal revolution was effected by the forward quarter inches apart, connected, as usual, by rush of the expelled fluid towards the angle staybolts. The side legs are about seven made by the front and starboard side, this feet, and the middle leg two and a half feet part of the front appearing to be pushed high. To admit the water into these legs, outwards. The boiler evidently fell first the cylinder, or belly of the boiler, is cut upon the hind and upper larboard corner, away by rectangular apertures at frequent which is seen to be much crushed, while the intervals. The lower half of the cylinder is explosion operated most powerfully on the occupied by forty-seven tubes, eight inches front and lower starboard corner. These in diameter, through which the smoke and two corners are diagonally opposite to each flame are returned forwards, from the cham other, and this circumstance may account, ber at the back of the boiler towards the (in connexion with the entanglement of the chimney in front. Between and above the boiler in the fragments of the upper deck,) rows of tubes were round tie-rods, three for the rotation. As the boiler lay in the fourths of an inch diameter, horizontal and hold on its larboard side after the explosion, crosswise to the cylinder ; but similar rods the starboard and middle legs, together with could not be introduced vertically between the portions of the cylinder between them, the tubes, on account of the spaces between were not entirely detached, but were so far them not coming in a line over each other. bent backwards, and curled over, as to emThus, the top and bottom of the cylinder brace the circular top; and, previous to the were not stayed by direct ties connecting raising of the boiler out of the sunken hull them in the position of chords; but the top of the vessel, they had to be separated by angles at either end of the boiler were braced the chisel. The cutting of the apertures







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over the legs, in the manufacture of the ing off the sheet-iron between the holes, and boiler, to admit the water into them, left the in a line with their centres. That it may be segments of the cylinder, between the legs, indifferent, so far as dimensions are conunited only by the strips of sheet metal re cerned, in which of these three ways the maining, and of these strips not more than joint may separate, there must be certain one-half the original number are left, the fixed proportions between the diameter of rest being carried away by the explosion. the rivet, (the head of which we will suppose The other injuries received were partly due to have always such an excess of strength, to the rupture, and partly to the fall of the as to make the shank of it give way first,) boiler; and the numerous and extensive the clear distance between the rivet holes rents manifest the insufficiency of the open and the edge of the plate, and the clear dising first made, though large, to vent the tance between the holes themselves, the confined fluid, and that the destruction, once thickness of the sheet being, of course, a begun, proceeds ad libitum, as in almost all constant element. Let us now see whether, similar cases.

in the riveting of the sheets of this boiler,

the correct proportions were observed. 1. The construction of the boiler, and the The rivets are eleven-sixteenths of an inch manner of its destruction, having been thus in diameter, and each has a transverse secdescribed, I proceed to estimate its strength tional area of 0:375 of a square inch, and, from the data I have procured, together, and there being three rivets to every strip of six in comparison, with the probable pressure of inches wide, the whole area of the rivets will the steam at or near the time of the explo be 1.125 square inches ; 2. The line of metal sion; and to state the facts of which I re left between the holes will be (6 – 2:062)= ceived information, respecting some of the 3.938 inches wide, which multiplied by onecircumstances of the accident, accompanied fourth of an inch, (the thickness of the by such remarks as have suggested them sheet,) will give an area of 0.985 of a square selves to me, in regard to its causes and inch; 3. The clear distance of the holes effects.

from the edge of the sheet is one and a The weakest part of the boiler, to which quarter inch, which, multiplied by onethe calculation must evidently be applied, fourth of an inch, gives an area of 0.312 of was manifestly the part of the cylinder im a square inch, and for the three holes, a total mediately over the legs, where the continuity area of 0.936 of a square inch. The three reof the sheets was interrupted by the aper sistances appear thus to be somewhat unequal, tures made in them to let the water down that of the rivets bei the greatest, by 14 into the legs, and promote its circulation per cent., of the strength of the metal between throughout the vessel. One-half of the the holes, and 20 per cent. of that of the metal strips of iron left between these apertures between the holes and the edge of the sheet. has been carried away, and the measured But when it is recollected that in the first case width of those that remained is irregular ; the rivet loses part of its whole strength by but there is enough to show that the united the strain it suffers in cooling, after being breadth of all the strips did not exceed that headed in a heated state, and that in the of the spaces between them, so that the third case the tearing out of the metal inboiler was not more than half as strong over volves more than the mere separation of the the legs as elsewhere, ceteris paribus. Thus, area of resistance, inasmuch as to permit in every twelve inches of the length of the this, the metal must be considerably bent on cylinder there were but six inches of sheet. either side of the line of rupture through iron to unite the segments separated by the which the rivet makes its way out, and as legs. A further reduction of strength, in furthermore, the friction of the lapping surthe connexion of these segments, was again faces of the plates augments their opposition made by the occurrence of seams in the to a separation by sliding on each other, it strips, depending on rivets, and weakened would seem as if the three resistances were by the holes punched for their insertion. very near to a practical equality, and that Now, the strength of a joint of this kind the sizes, numbers, and positions of the will depend upon the resistance of the rivets, rivet holes were about what they should be, and also on that of the remaining iron of the for the required equilibrium between the plates which they unite ; which resistances parts of the joint. Other boilers which I should manifestly balance each other, to give have examined show a similar adjustment of the maximum of strength to the joint. The parts in the joints, so that the general pracplates may be separated in three ways : 1. tice would seem to accord with the concluBy cutting off, or tearing asunder the rivets, sions of the present calculations. An inor tearing off their heads; 2. By splitting spection of the manner in which the plates and tearing out the metal between the rivet of the Medora's boiler separated at the holes and the edge of the sheet ; 3. By tear seams, showed that, in most instances, the

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